1. Field of the Invention
The present invention relates to an indexable insert with nicks to be used as a cutting edge for a rotary tool, such as a face milling cutter or an end mill.
2. Description of the Related Art
A known indexable insert includes an insert (an indexable insert with nicks) in which a plurality of nicks divides a ridge line of a cutting edge in a longitudinal direction and hence the ridge line is made rough. Such an insert with nicks is provided mainly as a cutting edge for a rotary tool. A face milling cutter employs an interrupted cutting edge as a main cutting edge (peripheral cutting edge). In use of such a rotary tool, the insert with nicks provided on the outer periphery of a tool body (cutter body) is arranged by shifting the phase of nicks of a former insert from the phase of nicks of a latter insert (so-called step arrangement) so that the latter insert complementarily cuts a remaining portion which has not been cut by the former insert in a comb like manner.
For example, inserts with nicks of related art are disclosed in, for example, Japanese Examined Utility Model Registration Application Publication No. 6-7856 and Japanese Unexamined Patent Application Publication No. 2006-305716. In a throw-away insert disclosed in Japanese Examined Utility Model Registration Application Publication No. 6-7856, a groove (in the specification, the groove is called nick) that divides a main cutting edge in a comb-like manner is provided on a flank face to extend in a direction obliquely intersecting with the main cutting edge. The groove (nick) has an end in the flank face, has a constant width from the position of the cutting edge to the end, and has a width gradually decreasing in a depth direction. The insert disclosed in Japanese Examined Utility Model Registration Application Publication No. 6-7856 is a so-called vertical insert having a side surface serving as a rake face, and upper and lower surfaces serving as flank faces.
In the throw-away insert disclosed in Japanese Unexamined Patent Application Publication No. 2006-305716, a nick that divides a main cutting edge is provided in a side surface. The insert disclosed in Japanese Unexamined Patent Application Publication No. 2006-305716 is used in a so-called horizontal position, in which upper and lower surfaces serve as rake faces, and a side surface serves as a flank face. That point is different from the insert disclosed in Japanese Examined Utility Model Registration Application Publication No. 6-7856. The nick extends from the edge at the upper surface to the edge at the lower surface (that is, the nick completely extends across the side surface of the insert in an insert thickness direction). This point is also different from Japanese Examined Utility Model Registration Application Publication No. 6-7856.
The throw-away insert disclosed in Japanese Examined Utility Model Registration Application Publication No. 6-7856 attempts to provide the following advantages. In particular, a cutting force is reduced by machining while the interrupted cutting edge divides chips. The cutting force is further reduced by inclining the nick with respect to the main cutting edge by an angle substantially equivalent to the angle of an axial rake of the cutting edge, by making the width of the nick constant, and by decreasing the width of the nick toward the bottom of the nick. Cutter vibration is reduced by reducing an impact during cutting. However, it is difficult to reliably provide a relief of the surface of the nick for the constant width of the nick. Therefore, depending on a cutting condition (for example, when a feed is increased), the surface of the nick contacts a workpiece, and hence a sufficient function is not provided. The machining condition may be narrow.
In the vertical insert with nicks in which the side surface having a greater area than that of the upper surface serves as a flank face, the nick depth direction is the insert thickness direction. The nick should not extend to the end of the flank face in the tool rotating direction so as to secure the strength of the insert. Hence, the insert is inclined in a direction in which the radial rake of the rake face approaches zero or in a direction in which a negative angle of the radial rake is increased in a view along a section perpendicular to the axis of the tool until the end of the nick does not interfere with the workpiece. The decrease in the radial rake of the rake face is limited. Owing to this, the substantial radial relief of the nick is limited within a small range. This also narrows the machining condition.
In the horizontal insert disclosed in Japanese Unexamined Patent Application Publication No. 2006-305716, the nick less affects the strength of the insert as compared with the vertical insert. Accordingly, the nick may extend from the upper surface to the lower surface. However, the nick receives a cutting force in the thickness direction. The insert is not suitable for heavy duty cutting.